What is lissencephaly?
A typical scan of a human’s brain will reveal many complicated wrinkles, folds, and grooves. This is how the body packs a large amount of brain tissue into a small space. The brain starts to fold during fetal development.
But some babies develop a rare condition known as lissencephaly. Their brains don’t fold properly and remain smooth. This condition can affect a baby’s neural function and symptoms can be severe.
What are the symptoms of lissencephaly?
Babies born with lissencephaly may have an abnormally small head, a condition known as microlissencephaly. But not all babies with lissencephaly have this appearance. Other symptoms may include:
- difficulty feeding
- failure to thrive
- intellectual impairment
- malformed fingers, toes, or hands
- muscle spasms
- psychomotor impairment
- trouble swallowing
It’s possible to perform imaging scans on a fetus as early as week 20 if one or both parents have a family history of lissencephaly. But radiologists may wait until 23 weeks to perform any scans.
What causes lissencephaly?
Lissencephaly is often considered a genetic condition, though sometimes a viral infection or poor blood flow to the fetus may cause it. Scientists have identified malformations in several genes as contributors to lissencephaly. But research into these genes is ongoing. And mutations in these genes cause varying levels of the disorder.
Lissencephaly develops when a fetus is 12 to 14 weeks old. During this time nerve cells begin to move to other areas of the brain as it develops. But for fetuses with lissencephaly, the nerve cells don’t move.
The condition can occur on its own. But it’s also associated with genetic conditions such as Miller-Dieker syndrome and Walker-Warburg syndrome.
How is lissencephaly diagnosed?
If a baby experiences symptoms related to incomplete brain development, a doctor may recommend an imaging scan to examine the brain. This includes ultrasound, CT, or MRI scans. If lissencephaly is the cause, a doctor will grade the disorder to the degree that the brain is affected.
Brain smoothness is called agyria, and brain groove thickening is called pachygyria. A grade 1 diagnosis means that a child has generalized agyria, or that most of the brain is affected. This occurrence is rare and results in the most severe symptoms and delays.
Most children affected have grade 3 lissencephaly. This results in thickening on the front and sides of the brain and some agyria throughout the brain.
How is lissencephaly treated?
Lissencephaly can’t be reversed. Treatment aims to support and comfort affected children. For example, children who have difficulty feeding and swallowing may need a gastrostomy tube inserted into their stomachs.
If a child experiences hydrocephalus, or an excessive accumulation of cerebrospinal fluid, surgery that shunts fluid away from the brain may be necessary.
A child may also need medications if they experience seizures as a result of lissencephaly.
What is the outlook for someone with lissencephaly?
The outlook for a child with lissencephaly depends on the condition’s severity. For example, severe cases may result in the child failing to develop mentally beyond a three- to five-months old function.
Children with severe lissencephaly have a life expectancy of about 10 years, according to the National Institute of Neurological Disorders and Stroke. Common causes of death include choking on foods or fluids (aspiration), respiratory disease, or seizures. Children with mild lissencephaly can experience near-normal development and brain function.